1. Field of the Invention
The present invention relates to improvements in a method and apparatus for measuring blood pressure by detecting Korotkoff sounds.
2. Discussion of the Prior Art
There has been known the technique of detecting with a microphone Korotkoff sounds which are produced from a living body synchronously with heartbeat of the body by pressing a portion of the body, and determining blood pressure based on the detected Korotkoff sounds. Recently this technique is used for continuously and regularly measuring blood pressure of a subject while the subject is doing physical exercise.
In the case of measuring blood pressure of a subject who is doing physical exercise by the technique in question, however, the detected Korotkoff sounds tend to include noise resulting from the exercise. In other words, a frequency range of the Korotkoff sounds overlaps that of such noise. Thus, accuracy of the blood pressure measurement has been unsatisfactory. The noise includes sounds produced by friction or rubbing of an inflatable cuff and sounds produced by striking or collision of hands, feet and other body members, both of which are compararively large and therefore troublesome, namely, tend to be detected by the microphone together with Korotkoff sounds. Thus, the detected Korotokoff sounds are not satisfactory to be used for blood pressure measurement.